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.\" Author: Archie Cobbs <archie@FreeBSD.org>
.\" $Whistle: ng_tee.8,v 1.4 1999/01/25 23:46:27 archie Exp $
.\"
.Dd May 28, 2004
.Dt NG_TEE 4
.Os
.Sh NAME
.Nm ng_tee
.Nd netgraph ``tee'' node type
.Sh SYNOPSIS
.In sys/types.h
.In netgraph/ng_tee.h
.Sh DESCRIPTION
The
.Nm tee
node type has a purpose similar to the
.Xr tee 1
command.
.Nm Tee
nodes are useful for debugging or
.Dq snooping
on a connection
between two netgraph nodes.
.Nm Tee
nodes have four hooks,
.Dv right ,
.Dv left ,
.Dv right2left ,
and
.Dv left2right .
All data received on
.Dv right
is sent unmodified to
.Em both
hooks
.Dv left
and
.Dv right2left .
Similarly, all data received on
.Dv left
is sent unmodified to both
.Dv right
and
.Dv left2right .
.Pp
Packets may also be received on
.Dv right2left
and
.Dv left2right ;
if so, they are forwarded unchanged out hooks
.Dv right
and
.Dv left ,
respectively.
.Sh HOOKS
This node type supports the following hooks:
.Bl -tag -width ".Va left2right"
.It Va right
The connection to the node on the right.
.It Va left
The connection to the node on the left.
.It Va right2left
Tap for right to left traffic.
.It Va left2right
Tap for left to right traffic.
.El
.Sh CONTROL MESSAGES
This node type supports the generic control messages, plus the following.
.Bl -tag -width foo
.It Dv NGM_TEE_GET_STATS Pq Ic getstats
Get statistics, returned as a
.Dv "struct ng_tee_stats" .
.It Dv NGM_TEE_CLR_STATS Pq Ic clrstats
Clear statistics.
.El
.Sh SHUTDOWN
This node shuts down upon receipt of an
.Dv NGM_SHUTDOWN
control message, or when all hooks have been disconnected.
If both
.Dv right
and
.Dv left
hooks are present, node removes itself from the chain gently,
connecting
.Dv right
and
.Dv left
together.
.Sh SEE ALSO
.Xr tee 1 ,
.Xr netgraph 4 ,
.Xr ngctl 8
.Sh HISTORY
The
.Nm
node type was implemented in
.Fx 4.0 .
.Sh AUTHORS
.An Julian Elischer Aq Mt julian@FreeBSD.org
